Power-operated hack saw



N0V 11, 1952 A. M. ROBERTS POWER-OPERATED HACK sAw 3 Sheets-Sheet lOriginal Filed May 29, 1948 ATTORN EY.

Nov. 11, 1952 A. M. ROBERTS POWER-OPERATED HACK sAw- 3 Sheets-Sheet 2Original Filed May 29, 1948 5? 64 6! 49 lNVENToR.

ATTORNEY.

Nov. l1, 1952 A. M. ROBERTS PowER-oPERATE HACK sAw Original Filed May29, 1948 HIIHHIIIH fred AT`ToRN EY.

Reissuecl Nov. 1l, 1952 POWER-OPERATED HACK SAW Alfred M. Roberts,Hamburg, N. Y.

Original No. 2,563,069, dated August 7, 1951, Sc-

rial No. 30,128, May 29, 1948. Application for reissue August 5, 1952,Serial No. 302,859

Matter enclosed in heavy brackets appears in the original patent butforms no part of this reissue specification; matter printed in italicsindicates the additions made by reissue.

11 Claims.

This invention relates to improvements in power operated hack saws andproposes a construction Which is especially applicable for use in therepair of pipe lines in situ, e. g., water or gas lines, in suchoperations as the substitution of new sections for rusted o-r brokensections or the repair, replacement or original location of valves.

In such operations, in the absence of a manhole, a ditch must be dug toexpose the section of the line in which the repair is to be made.Heretofore workmen, positioned in the ditch or man-hole, have cut thepipe sections with manually operated hack saws. very laborious and timeconsuming and, therefore, highly uneconomical. Moreover, the Workmen,conducting the manual sawing operations in restricted space, andfrequently in cramped positions, have been subject to undue physicaldiscomfort. If, as frequently happens, the ditch contains water, thephysical discomfort of the workman is increased by the necessity ofsquatting, cro-uching or stooping, with his feet in the water or mud,for the prolonged periods required by the work.

The structural characteristics of standard power driven hack saws are-such that they cannot be used in the environment described for repairsof the character described. Within a long career devoted to municipalwater and gas engineering projects I have not become aware of any powerdriven hack saw which can be satisfactorily used for the repair of pipelines in situ.

Power driven hack saws in accordance with the invention will be made inVarious sizes, each appropriate for a particular range of diameters ofpipe sections; and in each instance will be available for a wide rangeof diameters. Thus the smallest size will be available, for example, forypipes from four to eight inches in diameter; the next larger size forpipes from six to fourteen inches in diameter; the next larger size forpipes from twelve to twenty inches in diameter; the next larger size forpipes from eighteen to twenty-four inches in diameter; and so on throughthe range of larger diameters.

A power driven hack saw in accordance with the invention, and for thepurpose of the use described, is characterized: (1) by a guide unit andan associated hack saw unit movable relatively to the guide unit, theguide unit being securely clamped .to the pipe and being of suchconstruction that it effectively maintains the alinement of the saw withthe kerf, resisting any tendency of the combined units toward twistingThe work has been about a vertical axis, canting about a horizontalaxis, or displacement relatively to the pipe-as an axial center; (2) bythe compactness of the units and their compendious association wherebythe saw may be used in ditches of no greater extent than has heretoforebeen required, according to the diameter of the pipe section to berepaired, for manual hack saw operations; (3) by the arrangement of theclamping elements wholly at one side of the saw whereby, ascircumstances may require, a cut may be made very close to the end of apipe or to a valve or fitting; (4) by the direct application of power toan end of the saw whereby the utilization of power is optimum anddisadvantageous conditions of leverage and torque are avoided; (5) bythe direct application of power to one end of the saw to effect movementthereof in both directions coupled with the association with theOpposite end of the saw of means for maintaining the saw at all timesunder tension, thereby to prevent buckling, whipping o-r'back-lash; (6)by the provision for a very short stroke of the saw as compared with thestrokes of standardv power operated hack saws, namely a stroke,according to the size of the saw, within a range of from one to two'inches, whereas standard power operated hack saws have a minimum strokeof the order of six inches, and by the provision of a very rapidoperating speed, coordinated to the length of the stroke, for examplefor a one inch stroke of the order of 400 reciprocations per minute andcorrespondingly somewhat less for strokes of greater length, whereasstandard power operated hack saws have for their minimum stroke anoperating Speed of the order or reciprocations per minute, thesefeatures greatly contributing to the compactness of the construction'andenabling the time of the sawing per inch to compare favorably with thetime of sawing per inch of a standard power driven hack saw with itsmuch longer stroke; (7) by the provision for the reciprocation ofthe sawelement in a plane parallel to the common plane of the guide standardsof the guide unit, thereby to eliminate any possibility of the lateraldisplacement of the pipe during the sawing operation:l (8)' by theprovision of means for positively controlling the feed of the saw intothe kerf, thereby to take the direct weight of the saw unit from theends of the kerf and to minimize liability of binding; (9) by a hack sawunit of maximum simplicity and lightness of weight whereby the unit isreadily portable from one position to another in the course of theparticular repair job; (l) by the separability of the guide unit and thehack saw unit and provision for their quick and facile association inoperative relation and disassociation from operative relation; and (il)by the provision for the ready disconnection of the hack saw unit fromthe saw element, whereby on any rare occasion that the saw element maybecome jammed it may be left in the kerf from which it can be readilyremoved, and by the provision for the quick and facile replacement ofthe saw element, or the substitution of a new saw element, in operativerelation in the hack saw unit.

By virtue of the above characteristics a power driven hack saw inaccordance with the invention accomplishes its work rapidly andefficiently, effecting a great saving of time as compared with manualhack saw repair operations, requires but minimum power, minimizes theliability of the jamming of the saw element, may be readily and quicklyyrestored to operative relation if. for any mechanically unpreventablecause, jamming of the saw element should occur, is readily portable frompoint to point in the course of a particular repair job, may be readilyand quickly set up with its parts in operativev relation to the pipe tobe repaired, saves. much time of the` workman, and spares the Yworkmanthe physical discomfort attendant upon manual hack sawing in repairingpipes in situ.

In the accompanying drawings:

Figure 1 is a rear elevation of a power driven hack saw in accordancewith the invention, and as in use. Y

Figure 2 is a side elevation thereof.

Figure 3y is a front perspective view thereof.

Figure 4 is a side elevation, partly broken away and with a cover plateremoved, showing the mechanism for effecting the reciprocation of thesaw element, the eccentric yoke being shown at the outwardv limit of itsmotion.

Figure 5A is a cross section'on the line 5-5 of Figurey 4.

Figure 6 is a detail elevation of the inner face of the leg of the hacksaw unit with which is associated the means for maintaining the sawunder tension, the saw element being shown in section,

' Figure '7 is a detail longitudinal sectional view on'the` line 'I-.-'|cf Figure 6.

Figure`8`is a fragmentary elevation looking at the inner vertical vfaceof the leg of the hack saw unit with which is associated the means forapplying power to the hack 4saw element.

Figure 9 is a detail horizontal section onV the line 9,-9 of Figure 4but showing the eccentric yoke at the inward limit of its motion.

Figure 10 is a detail horizontal section on the line Ill-'I0 of Figure'l but showing the hack saw element in a position corresponding totheposition in which it is shown in Figure 9.

Figures 9 and 104 are arranged in juxtaposed position in the drawing andconnected by a bracket to indicate that together they may be taken as ahorizontalsection across the machine along the combined lines 9--9 ofFigure 4 andv Ill- I0 of Figure '7.

The construction includes a hack saw unit, indicated generally atY I,and a, guide unit indicated generally at 2.

The guide unit comprises a pair of upright guide standards 3 which areconnected and` mutually braced by a transverse plate 4. the ends of, theplate 4 being rigidly connected, as by welding, to the standards 3 andthe plate being arranged at an elevation with respect to the standards 3such that its position will be above the pipe P to be repaired. The hacksaw unit includes a frame 5 of substantial inverted U-s'hape, the frameconsisting of a pair of vertical legs 6 and 1 and a cross bar 8extending between, and connecting, the upper ends of the legs 6 and 'I.The legs E and 'I are each provided on their front faces with a pair oflower and upper guide lugs 9 which are each formed between their upperand lower faces with an opening I0 to take over the standards 3. Theopenings I0 conform to the cross sectional outline and dimensions of thestandards and each communicates with a vertical slot II which extends tothe inner face of the lug 9 and provides a clearance to accommodate theplate 4, thereby to enable the hack saw unit to be moved in eitherdirection along the post 3 through such extent as may be required. Withthe lugs 9 fitted upon the standards 3, the two units will be rigidlycoupled against displacement inall directions except relative slidingdisplacement in either direction of the standards. The hack saw unit isfreely slidable in either direction along the standards 3 and the twounits may be quickly and easily separated simply by pulling thestandards from the lugsl 9 and as easily and quickly restored tooperative relation by inserting the standards through the lugs 9 to therequired extent.

The hack saw elementl I2, in the form of the usual fine-toothed blade,extends transversely between the lower ends ofthe legs 6 and 1 and ismounted for' transverse reciprocation relatively to the frame 5. As willbe later described, the hack saw element I2 is mounted in a trulyhorizontal position and is at all times positively maintained forreciprocation in a truly horizontal path. The plane in which the sawelement I2 recip-rocates is parallel to the common plane of thestandards 3. The power for the operation ofthe element I2 is applieddirectly to one end thereof, the power applying mechanism, des-V ignatedgenerally as I3, being mounted at the lower end of theleg E and forminga part of the hack saw unit. The mechanism I3 is coop-era-` tive with atensioning mechanism, designated generally at I4, which is mounted atthe lower end of` the leg '1. forms a part of the hack s aw unit, andyis directly connected to the end of the element I2. opposite to the end,to which power is applied.

The guide. unit 2 is rigidly clamped to and upon the pipe P. One elementof the-clamp consists of a saddle which comprises a pair of plateshaving their lower edges of inverted V formation for two-pointengagement with the pipe. The plate 4 above described, isutilized as oneof the saddle plates, its lower edge of inverted V-shape being indicated'at I5. The second saddle plate I6 has a lower edge of inverted V-shapeas indicated at I'I. The plate I6l is located behind the plate 4and thetwo arerigidly connected, preferably by avcentral web I8. V-shaped edge,I'I accords with the particular range of diameters of pipe sections forwhich, according to its size, the. hack saw is designed to beY used.They edges I5 and II are of thesame angularity and corresponding legsoftheir Vs are co-planar. Thus when the saddle is tted to the pipeP thetwo plates 4 and I6 will conjointly provide four points of. clampingcontact. with the pipe, these points preferably delimiting a rectangle.The element of thel clamp companion The extent of ther to the saddleconsists of a chain I9 connected to the saddle and which is drawn tightabout the pipe in order to cooperate with the plates 4 and |6 inexerting clamping pressure upon the pipe.

The means of connection between the chain I9 and the saddle includes apair of rockably mounted bars 20 having end trunnions for which theplates 4 and I6 are formed to provide bearings, the bars 2D extending inparallel relation between these plates. The bars 20 each carry adownwardly projecting hook 2|, the threaded shanks of which extendthrough openings formed diametrically in the bars with their upperportions projecting beyond the bars and provide with retaining andtake-up nuts 22. The chain I9 is looped about the pipe P in oppositionto the saddle and drawn as tightly as possible manually against the pipewhereupon links thereof are engaged with each of the hooks 2 I Anyinitial slack is taken up by adjusting the hooks 2| upward relatively tothe bars 28, such adjustment being effected by turning the nuts 22 asfar as possible in the appropriate direction. At such time the chain I9is bound with the utmost security against the pipe and, in cooperationwith the plates 4 and I1, effects the clamping of the guide unit to thepipe with such rigidity that displacement of the guide unit in anydirection is prevented. Since the guide unit and the hack saw unit, asfitted upon the standards 3, are rigidly coupled against displacement inall directions, the alinement of the hack saw element with respect tothe kerf which it forms in the pipe will be positively maintained.

The hack saw unit is movable by gravity downward along the standards 3.However, it is preferred not to rely on gravity for the` downward feedof the hack saw element during the sawing operation but instead toprovide for the positive control of the downward movement of the hacksaw unit progressively with the sawing operation. For this purpose it ispreferred to provide a feed control screw 2-3 which carries a hand knob24. The screw 23 is vertically arranged at the center of the hack sawunit and has threaded engagement in the projecting arm of a supportingbracket 25 secured at a central location to the cross bar 8 of the frame5 and projecting upward from the cross bar. The upper` end of the screw23 carries the knob 24 and its lower end engages a lug 26 carried by andprojecting forward from the plate 4. The lug 26 thus provides verticalsupport of the saw unit from the guide unit. During the sawing operationthe attendant in chargeof the repair work grasps the knob 24 and turnsthe screw 23 in a direction appropriate to effect the downward slidingmovement of the saw unit relatively to the guide unit. The turning ofthe screw 23 to effect the downward feed of the saw unit is at a ratesuch that it will at once maintain the hack saw element I2 inappropriate contact with the ends of the progressively deepening kerfand will prevent the weight of the hack saw unit from being taken by theends of the kerf. The rate at which the screw 23 is turned for thesepurposes will be readily determined by the attendant from the sound madeby the element l2 in the sawing operation and also from the feeltransmitted to his hand through the knob 24.

The reciprocation of the hack saw element in a positively maintainedtruly horizontal path and in a plane parallel to the common plane of theguide standards 3, the constant positive maintenance of its alinementwith the kerf progressively 75;

6. with its deepening andv the'positive control of the downward feed ofthe saw unit eliminate all liability of the jamming or binding of thehack saw element except for mechanically unpreventable causes.

When the cut has been completed the-screw 23 is turned to lift the hacksaw unit relative to the guide unit to a position in which the hack sawelement clears the pipe P. The'chain I9 is then disengaged from thehooks 2| and the saw is moved along vthe ditch D (or within the chambernormally closed by a man-hole cover) to the position required for thenext cut to be made in the pipe, the guide unit thereupon being againclamped to the pipe as above explained. In thus shifting the position ofthe saw, the guide unit and hack saw unit may be left in connectedrelation or they may be separated, according to convenience. In smallersizes the weight of the two units will not be such as to interfere withtheir ready portability in connected relation. In larger sizes it may bepreferable to disconnect the units, the weight of each of which is notsuch as to interfere with their ready separate portability.

The mechanism I3 for the operation of the saw element I2 is arrangedwithin a housing designated generally as 21 and consisting of connectedtop, side and bottom walls 28, 29 and 30, respectively, and a coverplate 3| in a plane parallel to the plane of the side wall 29 andremovably secured by screws 32 to the lateral faces of the walls 28 and3D. The housing thus constituted is rigidly secured to the lower portionof the leg 6 from which it projects laterally outward, the walls 28, 29and 30 being preferably cast integrally with the leg G. The mechanism 3includes a reciprocatory yoke 33 mounted within the housing 2'1 andpreferably in the form of a vertical rectangular plate mounted fortransverse reciprocating movement between the walls 28 and 30 as upperand lower guides. The lateral guides for the yoke 33 are the cover plate3| and webs 34 and 35 (Figures 4, 8 and 9) integrally cast with thewalls 28, 29 and 30 of the housing 21. The walls 28 and 30, the coverplate 3| and the Webs 34 and 35 delimit a way in which the yoke 33 isreciprocatory, this way being open as at 3B (Figures 4 and 8) to theinner vertical face of the leg 6.

The walls 28, 29 and 30, theyoke 33 and the webs 34 and 35 delimit achamber 31 for the reduction gear which, in combination with the yoke,constitutes the mechanism I3. The reduction gear consists of a smallpinion 38 and a meshing larger pinion 39 in appropriate ratio. Thepinions 38 and 39 are mounted upon the ends of shafts 40 and 4|,respectively. The wall 23 is formed with projecting sleeves 42 and 43which provide bearings for the respective shafts 48 and 4|. The shaft 40projects for a suitable extent beyond its bearing sleeve 42 and issuitably connected, as by a flexible shaft (not shown), to a source ofpower, e. g., an electric motor (not shown). The plate which constitutesthe yoke 33, and in its capacity as such, is formed with a rectangularopening 44 and the pinion 39 is provided with a wrist-pin 45 cooperativewith the opening 44, the wrist-pin preferably carrying a standard ballbearing 46. the outer ring of which engages the walls of the opening 44.In the rotation of the pinion 39 the wrist-pin 45 via the ball bearing46 and the opening 44 eifects the reciprocation of the yoke 33 in theobvious and well known manner and the yoke 33 in its reciprocation movesthrough the opening 3i.

The hack saw element I2 at one end is con- 7, nected by a bolt fastening41 (Figures 4, 8 and 9) tothe yoke 33 adjacent its outer face, the plate3l being provided along its inner vertical edge with a recess 48(Figure 1) as a clearance for accommodating the adjacent end portion ofthe hack saw element I2 and the screw 41.

The reduction gearing 38--33 and the yoke 33 to which the hack sawelement I2 is directly connected by the screw 41 provide for thereciprocation of the hack saw element by power directly applied to oneend thereof. It will be seen that thereby there is an optimumutilization of power and that disadvantageous conditions attendant uponconsiderations of leverage and torque are eliminated.

The tensioning mechanism I4 is mounted upon the leg 1 at its lower endand is arranged within a housing 49 which projects laterally outwardfrom the leg. The tensioning mechanism includes a saw head 50 in theform of a cylindrical block provided at its inner end with a recess Iwhich affords a clearance for the adjacent end of the hack saw elementI2. Within the recess 5I the element I2 is connected to the head 5I) bya bolt fastening 52, the recess 5I having a flat vertical face againstwhich the end of the hack saw element bears. The head 5U is mounted toreciprocate in a guide sleeve 53, the inner end portion of which isfitted in a recess 54 at the lower end of the leg 1. outward beyond theleg 1 and is formed with a circumscribing collar 55 which bears againstthe outer side face of the leg. The collar 55 is externally threaded andthe casing 49 is formed at its inner end with internal threads to engagethe threads of the collar, the latter being thereby utilized to providesupport for the housing. The sleeve 53 is held against displacementabout its axial center and also against displacement from the recess 54by pins 56 carried by and projecting laterally outward from the sleeve 1and engaging in openings 51 in the collar 55. The saw head 50 is heldagainst displacement about its axial center by a radially projecting pin58 by which it is slidably keyed to the sleeve 53, the companion keyingelement consisting of a longi# tudinal slot 59 in the sleeve 53 andwhich extends to its outer end, the projecting part of the pin 53slidably engaging in the slot 59. A ring Si] is confined against theouter end of the head 50 and projects outward beyond the head to providean abutment for a helical compression spring 5I, the companion abutmentfor the spring 6I being provided by the collar 55. Th-e ring 60 is heldagainst the head 50 by a nut 62 having a sleeve-like extension E3 whichiits within an axial recess 64 at the outer end of the head 5D. Therecess 64 is countersunk to accommodate a screw 55 upon which the nut 62is mounted, the nut being internally threaded for engagement with thethreads of the screw.

The screw 65 is made fast to the saw head 55 whereby it will not turnabout its axial center or become axially displaced. For this purpose thepin 58 is utilized and is in the form of a screw, the end of whichengages a recess in the screw 63 and the head of which engages in theslot 59.

The nut 62 is normally held against turning upon the screw 65 by anysuitable means, for example a cotter pin 66 bearing against the outerface of the nut and tted in a diametrical opening in the outer endportion of the screw 65.

The compression spring BI reacts against the ring 6U to maintain thehack saw element I2 at all times under tension and also reacts againstThe sleeve 53 projects lateraliy the vcollar 55 to hold the'sleeve 53properly positioned upon the leg 1, in other words to hold the collaragainst the outer face of the leg and thereby to maintain the engagementof the pins 56 in the openings 61.

The bolt fastenings 52 and 41 are in horizontal alinement whereby thehack saw element is supported in a true horizontal position and isreciprocatory in a true horizontal path. This relation is maintained atall times because the mechanisms I3 and I4 are supported by rigid partsof the frame 5 of the hack saw unit, and therefore, as the hack saw unitis fed downward by the manipulation of' the screw 23 during the progressof the sawing operation the mechanisms I3 and I4 will move downward toan equal extent through positively maintained parallel vertical paths,all possibility of the hack saw element I2 being displaced from ahorizontal path or of bearing more strongly at one end of the kerf thanat the other being thereby positively eliminated.

If for any mechanically unpreventable cause the hack saw element I2should become jammed the hack saw unit may be quickly and easilydisconnected from the hack saw element, leaving the latter in its kerffrom which it may readih7 be removed, and the jammed hack saw element,upon removal from the kerf, if t for continued use, may thereupon bequickly and easily reconnected to the hack saw unit, or if necessary, anew hack saw element may be substituted. The disconnection of the hacksaw unit from a jammed hack saw element I2 is as follows; the= severalsteps being set forth in their order: One of the hooks 2| is backed offto slacken the chain I9 and permit its disengagement; the housing 49 isdisconnected from the collar 55; the bolt fastening 41 is disconnectedto free the hack saw element I2 from the yoke 33; the cotter pin 66 isremoved and the nut B2 is backed off to an extent sulicient to removethe compression of the spring 6I to a degree such that the sleeve 53 maybe pulled away from the leg 1 until the pins 5E are cleared; and theframe 5 of the hack saw l unit I, carrying with it the mechanism I3 inits housing 21 and also carrying with it the guide unit` 2, pulled awayfrom the hack saw element i2, in the axial direction of the pipe P,until the recess 54 has cleared the sleeve 53. At such time the jammedhack saw element I2 will be left in its kerf with the head 5I! attachedto it and the sleeve 53l spring 8|, ring 6I) and nut 52 in associationwith the head. As thus freed from the hack saw unit the jammed hack sawelement I2 may be readily removed from its kerf and, if in condition forfurther use, left connected to the head 50 and then, with the frame 5raised by the screw 23 to a suitable elevation above the pipe P,-reconnected to the yoke 33 by the fastening 41, the parts of thetensioning mechanism then being reapplied to the leg 1 and restored totheir normal operative relation. The housing 49 is then replaced and thesaw is properly repositioned upon the pipe P and clamped theretowhereupon the hack saw unit is lowered to reintroduce the hack sawelement into the kerf to the extent sufcient to enable the continuanceof the sawing operation. If the jammed hack saw element I2, upon itsremoval from the kerf, is found to be not in condition for further use,the sleeve is pulled back upon the head 50 to an extent sufficient toexpose the bolt fastening 52 and enable its disconnection in order tofree the hack saw element from the head 50. A new hack saw element isthen substituted. In some cases, hav-r .9' ing freed the hack sawelement from the jammed hack saw unit in the manner above described, itmay be found preferable in any event to substitute a new hack sawelement and clamp the saw in a different position upon the pipe P, closeto its former position, say for example, one-quarter of an inch away andstart a new kerf.

I claim:

1. A power operated hack saw for use in the repair of pipe lines in situcomprising, incombination, companion guide and hack saw units, the guideunit being provided with parallel vertical guide standards for locationat opposite sides of the pipe to be repaired and the hack saw unit beingprovided with guide lugs having openings to take over the standards, thehack saw unit thereby being slidable relatively to the guide unit ineither direction of the standards and parallel thereto and beingotherwise rigidly connected to the guide unit, means rigidly connectedto the guide unit for rigid clamping engagement with the pipe to berepaired, the hack saw unit including fixed Vparallel vertical legsextending adjacent opposite sides of the pipe to be repaired and locatedat one side of the guide standards and a cross bar rigidly connectingthe legs and located above the pipe to be repaired, the legs being in aplane parallel to the common plane of the guide standards, a hack sawelement extending transversely between and operatively movablerelatively to the lower ends of the legs, power operated actuating meanscarried by one of the legs and including a reciprocatory elementdirectly and detachably connected to an end of the hack saw element foreffecting its transverse reciprocation, said reciprocatory elementdirectly applying power to the hack saw element, and means carried bythe other leg and connected to the opposite end of the hack saw elementfor maintaining it under constant tension, said actuating means and saidtensioning means serving for the support of the hack saw element in itsposition between and transversely of the legs.

2. A hack saw as set forth in claim 1 wherein a vertical screw isprovided for regulating the downward feed of the hack saw unit, the hacksaw unit is provided with a bracket having threaded engagement with thescrew and the guide unit is provided with a lug against which the screwbears at its lower end.

3. A hack saw as set forth in claim 1 wherein the guide unit includes atransverse plate extending between and rigidly connected to thestandards and located behind the hack saw element and a secondtransverse plate located behind the plate rst named and rigidlyconnected thereto, each of the plates having its lower edge of invertedV-shape to provide two-point clamping engagement with the pipe to berepaired, the guide lugs having slots to accommodate said first namedplate during the movement of the hack saw unit along the guidestandards.

4. A hack saw at set forth in claim 1 wherein the actuating meansincludes a gear driven reciprocatory yoke directly attached to the hacksaw element and the leg which carries the actuating means is providedwith a housing which projects laterally outward and by which the yoke issupported and guided in its reciprocatory movement.

5. A hack saw as set forth in claim 1 wherein the actuating meansincludes a gear driven reciprocatory yoke, disconnectable means isprovided for the direct attachment of the hack saw element to thev yoke,lthe means for maintaining the hack saw under tension consists of a sawhead in the form of a block which is directly connected to the hack sawelement, a guide for the saw lhead in which it is reciprocatory, andcompression spring means at all timesacting on the saw head,disconnectable means is provided for the direct attachment of the hacksaw element to the saw head, the `leg which carries the means formaintaining the hackv saw'- element under tension is provided with arecess in lwhich the guide is mounted and from which it is removable,and means is provided 'for normally holding the guide in the recessofthe leg.,

6. A hack saw asset forth in claim 1 wherein the hack` saw-unitiand theguide unit are freely separable, the hack sawelement is detach'ablyconnected'to the actuating meansvand'tothe means for maintaining itunder tension and the means for maintaining the hack -saw element undertension is separable as a unit and in attached relation to the hack sawelement from the leg by which itis carried. 7. A power operated hack sawfor use inthe repair of pipelines-in situ comprising', in combination,companion guide and hack saw units having cooperating elements by meansof which the hack saw unit is slidable vertically in either directionrelatively to and parallel to the guide unit and is otherwise rigidlyconnected to the .guide unit, the hack saw unit including fixed parallelvertical legs and a horizontal reciprocatory hack saw element extendingtransversely between and movable relatively to the lower ends of saidlegs, means for the direct application of operating power and tensioningpower to the ends of the hack saw element, said means being carried bythe legs of the hack saw unit, supe porting the hack saw element andprescribing its reciprocation in the direction of its extent and meansfor rigidly clamping the guide unit to the pipe to be repaired.

8. A hack saw as set forth in claim 1 wherein the guide unit includes atransverse plate extending between and rigidly connected to thestandards and located behind the hack saw element the guide lugs havingslots to accommodate said plate during the moving of the hack saw unitalong the guide standards and the means for clamping engagement with thepipe is carried by the plate and is arranged wholly at one side of thehack saw element.

9. A power operated hack saw for use in cutting pipe lines in situcomprising, in combination, companion guide and hack saw units, saidguide unit being provided with parallel vertical guide standards forlocation at opposite sides of the pipe to be cut, a transverse plateextending between and rigidly connecte-d to said standards, said platebeing arranged at an elevation above the lower end of said standardswhereby said guide unit may be fitted over the pipe in situ, said hacksaw unit including parallel legs ertending adjacent opposite sides ofthe pipe to be cut and secured to said guide standards for verticalsliding movement in either direction relative and parallel thereto, across bar rigidly connecting said legs and located above the pipe to becut, a hack saw element mounted on said hack: saw unit for transversereciprocatory movement relative to the lower ends of said legs, poweroperated actuating means carried by one of said legs and including areciprocatory element drivingly connected to said hack saw element foreecting its transverse reciprocation, tensioning means carried by saidhaclc saw unit and connected to said hack saw element for maintainingthe latter under constant tension, and means carried by said guide unitfor rigidly clamping said guide unit to the pipe to be cut.

10. A power operated hack saw as set forth in claim 9, wherein saidmeans for rigidly clamping said guide unit to the pipe includes a secondtransverse plate rigidly connected to said guide unit and located on theopposite side thereof from said hack saw unit, each of said transverseplates having its lower edge of inverted V-shape to provide multi-pointclamping engagement with the pipe to be cut.

11. A power operated hack saw for use in the cutting of pipe lines insitu comprising, in combination, companion guide and hack saw unitshaving cooperating elements by means of which said hack saw unit isslidable vertically in either direction relative to and parallel to saidguide unit and is otherwise rigidly connected thereto, said guide unitincluding fixed parallel vertical standards disposed to extend onopposite sides of the pipe to be cut, said hack saw unit including ahorizontally reciprocable hack saw element disposed for transversemovement relative to said standards, means carried by said hack saw unitfor applying tensioning power to said haclc saw element, means carriedby said hack saw unit for applying actuating power to said hack sawelement, and means for rigidly clamping said guide unit to the pipe tobe cut, said last-named means including spaced transverse platespositioned on the guide unit side of said hack saw unit and rigidlyconnected to each other and to said guide unit, each of said plateshaving its lower edge shaped to partially embrace the pipe to be cutwhereby to provide a multi-point clamping engagement therewith.

ALFRED M. ROBERTS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,932,462 Howlett Oct. 31, 19332,011,623 French Aug. 2l), 1935 2,175,497 Wilbur Oct. l0, 1939 2,206,614OHern July 2, 1940 2,216,823 Paque Oct. 8, 194D

